Statement of problem

Currently many options are available for restoring a dental implant, although the ideal implant abutment for withstanding the occlusal load and the restorative material for fulfilling the esthetic need remains unclear. Zirconia (Zir) abutments offer good esthetics, but concerns still remain regarding their fracture strength, complex fabrication, and higher cost as compared with those of titanium (Ti) base abutments offering lower cost, acceptable esthetics, and a straightforward procedure.

Purpose

The purpose of this in vitro study was to evaluate the fracture strength and failure mode of single-tooth Zir and Ti base implant abutments with fatigue loading.

Material and methods

Forty restorations were included using 4 different types of abutment-restorations. Zir abutments with lithium disilicate crowns (ZirLd); titanium base abutments with custom Zir abutments and lithium disilicate crowns (TiZirLd); titanium base abutments with monolithic lithium disilicate abutment-crowns (TiLd); titanium base abutments with monolithic polymer-infiltrated ceramic abutment-crowns (TiEn). Specimens were subjected to a progressive cyclic loading by using a custom-made mastication simulator at a frequency of 1.4 Hz starting with a load of 88 N followed by stages of 170, 210, 250, and 290 N for a maximum of 20 000 cycles each or until fracture occurred. The number of cycles, maximum load, and failure modes were recorded. Statistical analysis was done by using the Mann-Whitney U test (α=.05).

Results

Group TiEn showed a lower resistance to fatigue, with a mean ±standard deviation of 5054 ±123.3 cycles subjected to a mean force of 170 N. Groups ZirLd and TiLd resisted higher forces without fracture 13452.6 ±7094.3 cycles, and load of 178 ±16.9 N, followed by the TiLd group with a mean ±standard deviation of 25798.6 ±5498.7 cycles, and load of 202 ±16.9 N, while the TiZirLd group showed a mean of 48235.4 cycles subjected to a mean force of 258 N. The failure mode observed in the TiEn occurred only in the ceramic, whereas in the ZirLd and TiLd group, it was above the shoulder level of the Ti base abutment. Even though the TiZirLd group was able to withstand higher loads and a higher number of cycles, the failures were catastrophic and presented fractures of the titanium-base abutment and prosthetic screw.

Conclusions

The TiZirLd, ZirLd, and TiLd abutment-restorations have the potential to withstand the average physiological occlusal forces that occur in the anterior region. The group with the higher fatigue resistance was TiZirLd, although care should be taken with patients presenting parafunctional habits since the failure mode can be catastrophic. Also, polymer-infiltrated ceramic is not suitable for a Ti base abutment when subjected to oblique loading.

中文翻译：

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不同陶瓷种植体基台疲劳载荷和失效模式的影响

问题陈述

目前有许多选择可用于修复牙种植体，尽管用于承受咬合负荷的理想种植体基台和满足美学需求的修复材料仍不清楚。氧化锆 (Zir) 基台具有良好的美观性，但与成本更低、美观性和操作简单的钛 (Ti) 基台相比，其断裂强度、复杂的制造和更高的成本仍然令人担忧。

目的

这项体外研究的目的是评估疲劳载荷下单齿锆和钛基种植体基台的断裂强度和失效模式。

材料与方法

包括使用 4 种不同类型的基台修复体的 40 种修复体。带二硅酸锂冠的 Zir 基台 (ZirLd)；带有定制 Zir 基台和二硅酸锂冠 (TiZirLd) 的钛基基台；具有整体式二硅酸锂基台冠 (TiLd) 的钛基基台；带有整体聚合物浸润陶瓷基台冠 (TiEn) 的钛基基台。通过使用定制的咀嚼模拟器以 1.4 Hz 的频率对样品进行渐进式循环加载，从 88 N 的负载开始，然后是 170、210、250 和 290 N 的阶段，每个阶段最多 20 000 个循环或直到发生骨折。记录循环次数、最大负载和故障模式。使用 Mann-Whitney U 检验 (α=.05) 进行统计分析。

结果

TiEn 组表现出较低的抗疲劳性，平均±标准偏差为 5054 ±123.3 个循环，承受 170 N 的平均力。ZirLd 组和 TiLd 组在 13452.6 ±7094.3 个循环和负载 178 ±16.9 N 的情况下抵抗更高的力而不断裂，其次是 TiLd 组，平均±标准偏差为 25798.6 ±5498.7 个循环，负载为 202 ±16.9 N，而 TiZirLd 组显示平均 48235.4 个循环，平均受力为 258 N。 TiEn 仅出现在陶瓷中，而在 ZirLd 和 TiLd 组中，它在 Ti 基台肩部水平以上。尽管 TiZirLd 组能够承受更高的负荷和更多的循环次数，但故障是灾难性的，并出现了钛基基台和修复螺钉的断裂。

结论

TiZirLd、ZirLd 和 TiLd 基台修复体具有承受发生在前部区域的平均生理咬合力的潜力。具有较高抗疲劳性的组是 TiZirLd，尽管由于故障模式可能是灾难性的，因此应注意表现出功能异常习惯的患者。此外，聚合物渗入陶瓷在承受倾斜载荷时不适合用作 Ti 基台。